The invention pertains to a method of manufacturing an adhesive fastener with a plurality of interlocking means in the form of stems having thickened parts at their terminal end and formed in one piece with a substrate, in which process a shapeable material in a plastic or liquid state is fed to the nip between a pressing tool and a shaping tool and these are driven such that the substrate is formed in the nip and conveyed in a transport direction, in which a screen having throughgoing cavities is used as the shaping element on the shaping tool, and in which the interlocking means are formed in that the shapeable material hardens at least partially in the cavities of the screen.
A method of this type has already been indicated as known in DE 196 46 318 A1. Disclosed as a possible application of an adhesive fastener produced in this manner is, in particular, the formation of an adhesive fastener for infant diapers or for hospital garments. For use in such articles of clothing a relatively large number of interlocking means per cm2 are required. In the known methods this leads to very high manufacturing costs for the shaping tool which, corresponding to the large number of interlocking means, requires a shaping tool with a correspondingly large number cavities per cm2. In order to guarantee that terminal thickened parts can be formed at the outer end of the stems formed by the impressed plastic, it is, moreover, necessary in the known processes for the screen cavities to have radii running inwards at their edges, at least on the side turned away from the pressing tool. By virtue of these radii, terminal thickened parts are formed on the stems, at least in rough form, already upon being filled with plastic.
The shaping of the very large number of cavities in the screen which are necessary for this, which can be accomplished by etching, galvanizing or by means of laser machining, leads to high manufacturing costs. The invention is therefore based on the problem of creating a method of this type that can be carried out with process equipment that is simpler and cheaper to produce and can therefore be carried out more efficiently.
In a method of the type mentioned initially, this problem is solved according to the invention in that a shaping tool is used such that it has a second shaping element interacting with its cavities on the side of the screen facing away from the pressing tool, by virtue of which element the shapeable material is formed in the area of the outer ends of the stems.
By the use of a second shaping element for structuring the terminal end of the stems, no particular demands are made on the geometry of the openings of the screen. In particular, the form and nature of the terminal areas of the stems formed by the filled-in material does not depend on the edge radii of the screen openings. This yields the advantage of a simpler and cheaper manufacturing of the screen.
Pressing tool and shaping tool can, as in the aforementioned known method, be provided as a pressing cylinder and a shaping cylinder, which are appropriately driven such that between them a conveyance gap is formed, through which the substrate is moved in the conveyance direction, where the shaping cylinder has the screen serving as the first shaping element on its outer side and the second shaping element is arranged in the inside on the cylinder body.
In a preferred embodiment, an internal second screen is used as the second shaping element arranged on the inside of the screen. If the cross-sectional size of the openings in the internal second screen are chosen to be somewhat larger than the cross-sectional size of the cavities of the first screen, then terminal thickened parts of the stems are formed upon filling in the plastic. The difference in cross section is chosen such that pulling out of the stems after setting or partial setting of the plastic can be done without difficulty. No elaborate machining to produce rounded corners is necessary for the cavities of the second screen either.
As the second shaping element arranged on the inside of the screen, a film provided with projections which extend into cavities of the screen is provided in a second embodiment, whereby depressions in the ends of the stems formed from plastic are generated during the filling of the thermoplastic material into the cavities. By virtue of the fact that the depressions in the formed stems are created in place of terminal thickened parts, there results the advantage of extremely simple extraction from the mold [cavities in the screen], without any particularly large extraction force having to be exerted.
Both in the example of forming terminal thickened parts and in the procedure of forming terminal depressions in the stems, mushroom shapes of the terminal thickened parts, advantageous for adhesive fasteners, can be achieved on the above-described stems by simple mechanical reshaping, by means of a heated or unheated calender, i.e., without a melting process having to occur.
By selecting the cross-sectional shapes of the cavities in the screen and/or the shape of the projections on the second shaping element, the terminal thickened parts of the stems can be formed, not only in the shape of mushroom tops that are flattened or have concave depressions, but also in polygonal or star shapes.
The object of the invention is also a sheet adhesive fastener which has the characteristics of claim 12.